feat: 重构 Dashboard 为卡片式分组布局

表格布局替换为按分组展示的卡片式布局，新增 group 字段配置和 TargetBoard/TargetCard 等组件。模态框详情页支持时间范围筛选和分页，SummaryCards 减为 3 个。API 端点变更：trend/history 改用 from/to 参数，history 支持分页。recentSampleCount 硬编码为 30。

src/web/components/StatusBar.tsx

@@ -0,0 +1,17 @@
+interface StatusBarProps {
+  samples: Array<{ up: boolean }>;
+}
+
+export function StatusBar({ samples }: StatusBarProps) {
+  const blocks = [];
+  for (let i = 0; i < 30; i++) {
+    const sample = samples[i];
+    if (sample) {
+      blocks.push(<span key={i} className={`status-bar-block ${sample.up ? "status-bar-up" : "status-bar-down"}`} />);
+    } else {
+      blocks.push(<span key={i} className="status-bar-block status-bar-empty" />);
+    }
+  }
+
+  return <div className="status-bar">{blocks}</div>;
+}